The cameo appearance came at the end of Waters’ concert at the United Center, the second of three shows there on his Us + Them North American. tour. Waters began the song with his band, as he would normally do. Some of the audience appeared to be unaware of Vedder’s presence on stage before the lighting changed as he began to sing, and Waters passed on a friendly word and pat on the shoulder before stepping out of the spotlight.

It’s not the first time the pair have shared a stage – they duetted on “Comfortably Numb” at the 12-12-12 concert in New York, held to raise funds for the victims of that year’s Hurricane Sandy. Pearl Jam have also performed the song in their own right on tour.

Waters is currently on the road supporting his new album, Is This the Life We Really Want? His tour's next stop is in St. Paul on Wednesday, followed by another date in Chicago on Friday. He'll remain in the U.S. until two nights in Boston on Sept.27- 28, at which point he'll spend the entirety of October performing throughout Canada. He can see all the dates at his website.